Improving the sensitivity of QEXAFS using modulation excitation spectroscopy

Modulation excitation spectroscopy (MES) is a promising tool to analyze time-resolved EXAFS data during reproducible catalytic processes and was applied in two different experiments to evaluate the benefits compared to conventional analysis strategies. Thereby, phase sensitive detection (PSD) was applied directly to the x-ray absorption spectra as well as to the Fourier transformed extracted EXAFS. In both cases the results were discussed with respect to the achievable level of noise reduction as well as the possibilities to better understand the underlying mechanisms of the reactions, more precisely the dynamics and possible intermediate species. The results clearly demonstrate serious limitations for the application of MES in time-resolved EXAFS studies as soon as more sophisticated steps than averaging over several modulation cycles are performed